Multi-unit intercom system

ABSTRACT

A multi-unit intercom system is disclosed in which a plurality of remote stations can be signaled from a common station. Switches are provided at the remote stations for persons located there to either control a two-way communications link between the particular remote station and the common station or operate an electrical device such as a door latch for admitting the person at the central station to a facility.

United States Patent 1 1 3,732,372

Tramontano 51 MayS, 1973 54] MULTI-UNIT INTERCOM SYSTEM 3,484,561 l2/l969 Matthews ..179 39 [75] Inventor: Frank Tramontano, FOIBSI H1118, PATENTS APPLCATIONS N.Y. I 1,279,759 10/1968 Germany ..179/2.9 [731 Assignecz E.R.L. Electronic Products, Inc.,

Forest Primary Examiner-Kathleen H. Claffy [22] Filed: S t, 14, 1971 Assistant Examiner-Kenneth D. Baugh Att0meyLemer, David & Littenberg [21] Appl. No.: 180,413

[57] ABSTRACT [52] 11.8. C1. ..l79/2 A, 179/37 A mummnit intercom System is disclosed in which a [51] h "H04m 9/02 plurality of remote stations can be signaled from a [58] Field of Searc ..I7 I39, 38, 37, l H, common Station Switches are provided at the remote 179/2 A stations for persons located there to either control a f two-way communications link between the particular [56] Re erences remote station and the common station or operate an UNITED STATES PATENTS electrical device such as a door latch for admitting the v person at the central station to a facility. 3,532,820 10/1970 Holm ..179/37 X 3,284,571 11/1966 Wittig ..179/2 A 10 Claims, 1 Drawing Figure I 4 1' y 191, an 3/6 {F4 m 4/1 2 //b 51a Ma 434 4/11 l 76c ml 1 44 v6 /7 f 11 #37 i Lm L o 1 r 1 "1? lZv /26 /3; 39 l 441 '6 A r r 1 a 25, 5 t l v I I T T -l L MULTl-UNIT INTERCOM SYSTEM FIELD OF THE INVENTION This invention relates to a multiunit intercom system and particularly to a multi-unit intercom system for use in high rise buildings and the like.

BACKGROUND OF THE INVENTION Many apartment buildings exist today in which a pair of wires extend from the lobby thereof up a line of apartments. These wires are connected to terminals in each apartment in the line. An additional wire extends from a panel in the lobby to each individual apartment. These wires have been used in the past for intercom systems. The original intercom systems which were employed used the single wire to control a buzzer which rang in the apartment when a button was depressed in the lobby. The pairs of wires connected microphones and earphones so that someone in the lobby could speak to a person in an apartment who responded to the buzzer. Some systems included an'additional switch in the apartment which the occupant thereof could actuate to actuate an electric door latch to allow a person in the lobby to gain access to the building.

These systems did not provide adequate voice communications because amplification was not included in the system. Therefore, people normally were required to shout into the microphone in order to be heard at the other end. Even with the shouting, the quality of the voice transmitted was poor.

Systems exist for voice communications in apartment buildings using additional wires. These systems, how-- ever, require a complete rewiring of the building which in many instances rendered the systems economically unfeasible.

Some attempts have been made to design systems which employ the existing wires in old apartment buildings to install voice intercom systems with amplifiers controlled by the occupant of the apartment. It has been found, however, that in these systems if the talk switch is pressed at certain times, the door latch will be accidentally operated. These systems also operate on voltage strength which means that if two or more persons in different apartments respond to a buzzer, the door latch may be accidentally tripped.

Therefore, it is an object of this invention to provide a new and improved multi-unit intercom system.

It is a further object of this invention to provide a multi-unit intercom system in which existing wiring in apartment buildings can be employed.

It is still a further object of this invention to provide a multi-unit intercom system in which an amplifier is switched at the control of the tennant.

It is yet another object of this invention to provide a multi-unit intercom system employing the existing wiring in apartment buildings which does not allow the granting of accidental access to the building.

BRIEF DESCRIPTION OF THE INVENTION With these and other objects in view the present invention contemplates a system in which a buzzer in each of a plurality of apartments is actuated by a switch in the lobby thereof. Switches in each of the plurality of apartments are provided for independently operating an electric door latch and an amplifier switching relay DESCRIPTION OF THE DRAWING The sole FIGURE is a circuit diagram of a multi-unit intercom system constructed in accordance with the teachings of this invention.

DETAILED DESCRIPTION OF THE INVENTION Referring now to the sole FIGURE, we see a schematic diagram of a multi-stationed intercom system constructed in accordance with the teachings of this invention. The system provides intercommunication between a lobby button panel 10 at a central station and a plurality of remote stations 11a, 11b and 110.

'Normally such a system would be employed in a high rise apartment building where the central station is located in a lobby and the remote stations are in the individual apartments. Additionally, circuitry is included in the system for permitting a tenant in any of the apartments to remotely unlock a door between the lobby and the apartment.

In order for a person in the lobby to signal a particular apartment, indicating a desire to speak with an individual therein, a plurality of single pole, doublethrow switches 12:; through 12c are mounted on a lobby button panel 10 which is normally located in the lobby of the building. A central voice transducer 13 which can serve either as a microphone or a speaker is also provided and normally mounted on or adjacent to the lobby button panel 10. A remote voice transducer 14a and 14b is located in each of the remote stations 11a and 11b for communicating with a person in the lobby. (It should be understood, of course, that each of the additional remote stations 11c and those not shown have identical equipment to each of the remote stations 1 1a and 1 lb shown in detail.)

A pair of conductors l6 and 17 extend from the lobby up a chain of apartments. The conductors 16 and 17 are connected to terminals (not shown) in each of the remote stations 11a, 11b, etc. A signaling conductor 18a through 18c runs from the lobby to each of the remote stations 11a, 1117, etc. A buzzer 19a and 19b is located in each of the remote stations 11a, 11b, etc. The systems further includes a remotely controlled electronic door latch relay 2] which maintains a door between the lobby and the remainder of the high rise apartment building locked until electrically energized or manually unlocking by a conventional key.

In accordance with this invention, the above elements located in 'a high rise apartment building are interconnected and powered by a power supply 22 to provide independent control over the various functions required. Control of voice communication is maintained in each of the apartments for the tenants convenience. The power supply 22 supplies a 'negative D.C. voltage at an output terminal 23 with respect to a reference terminal 24 and an A.C. voltage on an output terminal 26 with respect to the same reference terminal 24. The A.C. voltage provided at the output terminal 26 is supplied by a lead 27 to the normally opened contacts of each of the switches 12a through 12c. The D.C. voltage supplied on the output terminal 23 is applied by a lead 28. to the junction of the electronic door latch relay 21 and an amplifier switching relay 29. The reference terminal 24 is connected to the common conductor 16. Each of the conductors 18a, 18b and 18c are connected to the common pole of switches 12a through 120 and are connected in the remote stations 11a, 11b and 110 to the buzzers 19 a 19b, etc. by a diode 31a, 3111, etc. Each of the diodes 31a, 31b, etc. are poled in a first direction. The normally closed contact of the switches 12a through 120 are connected to the opposite side of the amplifier switching relay 29. The common conductor 17 is connected to the side of the electronic door latch circuit not connected to the power supply 22.

Looking now particularly at the remote station 11a (and remembering that each of the other remote stations have identical equipment therein), we see that a normally opened switch 33a is connected between the conductors 16 and 17. A double pole, double-throw switch 34a provides a first set of contacts for connecting the conductor 18a to the conductor 16 in a first normally opened position and maintains an open circuit therebetween in a nuetral position and in a second opened position. A second set of contacts on the switch 34a connects a circuit consisting of the voice transducer 14a and a capacitor 36a in series, across the conductors 16 and 17 in first and second normally opened positions and maintains an open circuit therebetween in its nuetral position.

In the systems dormant position (as shown), none of the devices (i.e., the amplifier switching relay 29, the buzzers 19a, 19b, etc. and the electric door latch relay 21) are operated. The diode 31a prevents current from flowing in the loop which includes the conductor 16, the buzzer 19a, the amplifier switching relay 29 and the lead 28 thereby rendering the buzzer 19a and the amplifier switching relay 29 inoperative. The normally opened switch 33a prevents the electric door latch relay 2] from being operated.

In' operation, a person in the lobbycan signal a particular apartment, for example the one associated with the remote location 1 1a, by operating the switch 12a to open-the normally closed contact and close the normally opened contact. In this way, a path is provided from the terminal 26 of the powersupply 22 through lead 27, the normally opened contact-of the switch 12a, lead 18a, diode.3la, buzzer 19a and conductor 16 back to the common reference terminal 24. Since an A.C. voltage is provided on the terminal 26, the diode 31a half wave rectifies the signal and provides a half sinusoid signal to operate the buzzer 190.

A person located in the apartment associated with the remote station Ila can communicate with a person in the lobby by actuating the switch 34a to the right in the figure. This connects the voice transducer 14a in series with the capacitor 36a across the conductors l6 and 17. A pair of capacitors 37 and 38 A.C. couple the conductors l6 and 17 respectively through contacts of the amplifier switching relay 29 to the output of an amplifier 39. The output of the amplifier 39 is connected through additional contacts of the amplifier switching relay 29 to the voice transducer 13. In this way a path is established by which a person in the apartment can listen to the voice transducer 14a and hear the person in the lobby speaking through the voice transducer 13.

By having the capacitor 36a in series with the voice transducer 140, no D.C path is established between the conductors 1 6 and 17. If a DC. path had been established, the electric door latch 21 would have been operated. It should be noted that the size of the capacitor 36a must be chosen sufficiently small so as not to momentarily operate the electric door latch 21 yet suf-v ficiently large so as not to audibly degrade the quality' of the speech transmitted.

If the'person in the apartment associatedwith the remote station 11a wishes to talk to the person in the lobby, he merely actuates the switch 340 to the left hand position as shown in the figure. It will be noted that the voice transducer 14a in series with the capacitor 36a are connected between the conductors 16 and 17 as they were when the switch was actuatedin the right hand position. However, when the switch is actuated in the left hand position, the conductors 18a and 16 are shorted by a lead 41a bypassing the diode 31a and the buzzer 19a. Current will now flow from the terminal 23 through lead 28, the amplifier switching relay 29, the normally closed contacts of the switch 12a, conductors 18a and 41a, contacts on the switch 34a and conductor 16 back to the terminal 24. This energizes the amplifier switching relay 29 to reverse the contacts associated therewith connecting the amplifier 31 with the its output thereof connected to the voice transducer l3 and the input thereof connected to capacitors 37 and 38.

In this way the amplifier 39 is now connected to amplify sounds from the voice transducer 14a to drive the voice transducer 13. It should be noted that control of who shall speak and who shall listen is in the remote station 11a so that a person in the lobby cannot either listen to or speak to a person in an apartment without the consent of the person in the apartment. Further, it should be noted that the voice transducer 14a is not connected across the conductors 16 and 17 when the switch 340 is in its nuetral position so that access cannot be gained thereto without operation by a person in an apartment. It should be further noted that each of the switches 12a, 12b and 12c, 3311,3317 and 330 and 34a, 34b and 340 are momentary contact switches which must be held depressed in order to actuate the circuits. Therefore the system as shown will always revert to its dormant state unless a switch is manually depressed.

If a person in the apartment associated with remote station 11a wishes to grant access to the building to the person in the lobby, he merely depresses the switch 33a which electrically connects the conductors 16 and 17. This provides a path from the terminal 24 of the power supply 22 through the conductor 16, the switch 33a,

are provided outside the apartment door. One side of the switch 42a is connected to the junction between the diode 31a and the buzzer 19a. The other side of the switch 42a is connected to the additional available wire 43a running to the lobby. in the lobby, the wire 43a is connected to the terminal 26 of the power supply 22. ln this case, an additional wire 44 is employed to connect the end of the wire 43a to the lead 27 and from there to the terminal 26. When the switch 42a is depressed, the A.C. voltage supplied on the terminal 26 rings the buzzer 19a with a full sinusoid voltage thereby providing a tone different than the one produced by the depression of the switch 19a which sent a half sinusoid voltage through the buzzer 19a. In this way, a person in the apartment can tell the difference between a buzz which is originating in the lobby and one which originates at the apartment.

It should be understood that while this invention has been described with respect to a specific embodiment thereof, numerous others will become obvious to those of ordinary skill in the art in light thereof.

What is claimed is:

1. A circuit for independently energizing first, second and third electrical devices each having first and second terminals with a power source supplying a DC voltagewith respect to a reference voltage and an AC voltage with respect to said reference voltage; said first, second and third electrical devices being operable parts of a multi-unit intercom system; said circuit comprising:

a first switch having first, second and third contacts, said first and second contacts being normally closed and said first and third contacts being normally opened; 2 1

means for connecting said second contact of said first switch to said first terminal of said first electrical device;

means for connecting said second terminal of said first electrical device to said DC voltage;

a first diode having first and second terminals;

means for connecting said first-terminal of said first diode to said first contact of said first switch;

means for connecting said third contact of said first switch to said AC voltage;

means for connecting said second terminal of said first diode to said first terminal of said second electrical device; I

means for connectingsaid .second terminal of said second electrical device to said reference voltage;

a second switch having first and second contacts that are normally opened;

means for connecting said first contact of said second switch to said reference voltage;

means for connecting said second contact of said a fourth switch having first and second contacts that are normally opened;

means for connecting said first contact of said fourth switch to said AC voltage; and

means for connecting said second contact of said fourth switch to said first terminal of said first electrical device.

3. The circuit as defined in claim 1 in which one of said first and third electrical devices is a relay, said circuit further comprising:

a first voice transducer; additional contacts on one of said second or third switches to connect said voice transducer between said reference potential and said first terminal of said third electrical device when said first and second contacts of said one of said second and third switches are in a closed position;

an amplifier having an input and an output;

a second voice transducer; and

contacts associated with said relay to connect (1) said input of said amplifier between said reference potential and said first terminal of said third electrical device and said output of said amplifier across said second voice transducer when said relay is deenergized and (2) said output of said amplifier between said reference potential and said first terminal of said third electrical device and said second voice transducer across said input of said amplifier when said relay is energized.

4. The circuit as defined in claim 3 also including:

a fourth switch having first, second and third contacts, said first and second contacts being normally closed and said first and third contacts being normally opened;

means for connecting said second contact of said fourth switch to said first terminal of said first electrical device;

a second diode having first and second terminals;

means for connecting said first terminal of said second diode to said first contact of said fourth switch;

means for connecting said third contact of said fourth switch to said AC voltage;

a fourth electrical device having first and second terminals;

means for connecting said second terminal of said second diode to said first terminal of said fourth electrical device;

means for connecting said second terminal of said fourth electrical device to said reference voltage;

a fifthvswitch having first and second contacts which are normally opened;

means for connecting said first contact of said fifth switch to said reference voltage;

means-for connecting said second contact of said fifth switch to said first terminal of said third electrical device;

a sixth switch having first and second contacts which are normally opened;

means for connecting said first contact of said sixth switch to said first contact of said fourth switch;

and

.means for connecting said second contact of said sixth switch to said reference voltage.

of said second or third switches is a momentary, contact switch normally in said second position.

7. The circuit as defined in claim 5 in which said one of said second and third switches is said third switch and said relay is said first electrical device.

8. The circuit as defined in claim 7 in which said third electrical device is an electric door latch.

9. The circuit as defined in claim 8 in which said second electrical device is a buzzer.

10. The circuit as defined in claim 9 in which said one of said second or third switches is a momentary control switch normally in said second position.

i i I I 

1. A circuit for independently energizing first, second and third electrical devices each having first and second terminals with a power source supplying a DC voltage with respect to a reference voltage and an AC voltage with respect to said reference voltage; said first, second and third electrical devices being operable parts of a multi-unit intercom system; said circuit comprising: a first switch having first, second and third contacts, said first and second contacts being normally closed and said first and third contacts being normally opened; means for connecting said second contact of said first switch to said first terminal of said first electrical device; means for connecting said second terminal of said first electrical device to said DC voltage; a first diode having first and second terminals; means for connecting said first terminal of said first diode to said first contact of said first switch; means for connecting said third contact of said first switch to said AC voltage; means for connecting said second terminal of said first diode to said first terminal of said second electrical device; means for connecting said second terminal of said second electrical device to said reference voltage; a second switch having first and second contacts that are normally opened; means for connecting said first contact of said second switch to said reference voltage; means for connecting said second contact of said second switch to said first terminal of said third electrical device; means for connecting said second terminal of said third electrical device to said DC voltage; a third switch having first and second contacts which are normally opened; means for connecting said first contact of said third switch to said first contact of said first switch; and means for connecting said second contact of said third switch to said reference voltage.
 2. The circuit as defined in claim 1 also including: a fourth switch having first and second contacts that are normally opened; means for connecting said first contact of said fourth switch to said AC voltage; and means for connecting said second contact of said fourth switch to said first terminal of said first electrical device.
 3. The circuit as defined in claim 1 in which one of said first and third electrical devices is a relay, said circuit further comprising: a first voice transducer; additional contacts on one of said second or third switches to connect said voice transducer between said reference potential and said first terminal of said third electrical device when said first and second contacts of said one of said second and third switches are in a closed position; an amplifier having an input and an output; a second voice transducer; and contacts associated with said relay to connect (1) said input of said amplifier between said reference potential and said first terminal of said third electrical device and said output of said amplifier across said second voice transducer when said relay is deenergized and (2) said output of said amplifier between said reference potential and said first terminal of said third electrical device and said second voice transducer across said input of said amplifier when said relay is energized.
 4. The circuit as defined in claim 3 also including: a fourth switch having first, second and third contacts, said first and second contacts being normally closed and said first and third contacts being normally opened; means for connecting said second contact of said fourth switch to said first terminal of said first electrical device; a second diode having first and second terminals; means for connecting said first terminal of said second diode to said first contact of said fourth switch; means for connecting said third contact of said fourth switch to said AC voltage; a fourth electrical device having first and second terminals; means for connecting said second terminal of said second diode to said first terminal of said fourth electrical device; means for Connecting said second terminal of said fourth electrical device to said reference voltage; a fifth switch having first and second contacts which are normally opened; means for connecting said first contact of said fifth switch to said reference voltage; means for connecting said second contact of said fifth switch to said first terminal of said third electrical device; a sixth switch having first and second contacts which are normally opened; means for connecting said first contact of said sixth switch to said first contact of said fourth switch; and means for connecting said second contact of said sixth switch to said reference voltage.
 5. The circuit as defined in claim 3 in which said one of said second or third switch has first, second and third positions; said first and second contacts thereof being closed in said first position and opened in said second and third positions; said first voice transducer being connected between said reference potential to said first terminal of said third electrical device when said switch is in said first and third positions.
 6. The circuit as defined in claim 5 in which said one of said second or third switches is a momentary contact switch normally in said second position.
 7. The circuit as defined in claim 5 in which said one of said second and third switches is said third switch and said relay is said first electrical device.
 8. The circuit as defined in claim 7 in which said third electrical device is an electric door latch.
 9. The circuit as defined in claim 8 in which said second electrical device is a buzzer.
 10. The circuit as defined in claim 9 in which said one of said second or third switches is a momentary control switch normally in said second position. 